1. Field of the Disclosure
The disclosure generally relates to silicone polymer fluids and silicone polymer fluid-containing compositions for sunscreening and photoprotection. More specifically, to silicone polymers containing pendant α-cyano-β,β-diphenylacrylate derivatives for the photostabilization of photoprotective (UV-absorbing) compounds.
2. Brief Description of Related Technology
Ultraviolet radiation (light) can cause various types of chronic and acute damage to human skin. Overexposure to ultraviolet light having a wavelength from about 280 nm or 290 nm to about 320 nm (UV-B) can produce sunburn, while chronic overexposure can lead to skin cancer and weakening of the immune system. UV-B radiation is capable of causing damage to DNA by chemically altering the DNA structure. Both UV-A radiation (about 320 nm to about 400 nm) and UV-B radiation can damage collagen fibers and vitamin A in the skin, leading to a reduction of skin elasticity and accelerated aging of the skin.
Additionally, ultraviolet radiation from the sun or artificial sources can damage coatings containing photoactive substances, such as photoactive pigments and dyes, by altering chemical bonds in the structure of a component, such as a polymer, a pigment, or a dye. This photodegradation can lead to color fading, loss of gloss, and loss of physical and protective properties of a coating.
The inclusion of UV-absorbing and photoprotective compounds in compositions such as sunscreens and coatings can serve to reducing the damaging effects of UV radiation. These photoprotective compounds are often chromophore-containing organic molecules but themselves are prone to photodegradation and, thereafter, can absorb little or no additional UV light. The photostabilization of these photoprotective molecules require the molecules to return to the ground state faster than the photodegradation occurs. There are known photostabilizing sunscreen additives, e.g. octocrylene, that quench the photoexcited state of sunscreening molecules. For example, octocrylene is known to photostabilize avobenzone.
The photostabilization of cosmetic sunscreen compositions containing dibenzoylmethane derivatives, e.g., avobenzone, requires at least 1% by weight of an α-cyano-β,β-diphenylacrylate, e.g., octocrylene, and a 4:5 mole ratio of the α-cyano-β,β-diphenylacrylate to the dibenzoylmethane derivative. Obviously, increasing the weight percentage of the photoprotective molecule in the composition requires an increase in the weight percentage of the photostabilizing molecule, but these increases can lead to degradation of cosmetic, and/or structural properties of compositions containing the molecules.
While octocrylene can photostabilize, to some degree, dibenzoylmethane derivatives, there still exists a need in the photoactive composition art to find one or more compounds that photostabilize photoactive materials. Moreover, enhanced photostabilizing compounds are needed for material and dermatologic protection.
Quite surprisingly, it has been found that silicon polymers containing α-cyano-β,β-diphenylacrylate groups, preferably alkoxy-substituted α-cyano-β,β-diphenylacrylate groups efficiently photostabilize UV-absorbing organic molecules even at low loadings compared to the quantity of UV-absorbing compounds. Additionally, the disclosed silicone fluids enhance the photoprotection provided by UV-absorbing organic molecules thereby lessening the required loading necessary to provide sufficient UV protection.